This application claims the priority of German patent document 196 53 522.0, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a process for transmitting energy and data, for example, from the steering column to the steering wheel of a vehicle. Flexible lines are predominantly used nowadays for this purpose. In the case of the steering wheel, a so-called flat spiral spring, however, is used for this purpose. The flat spiral spring has the disadvantage that it causes noises, is mechanically sensitive and, because of its construction, has unfavorable EMV characteristics.
No contact processes on an optical and inductive basis are also known. The optical processes have the disadvantage that they are susceptible to dirt; and higher powers (for example, for a steering wheel heater) cannot be transmitted.
In a process of the initially mentioned type disclosed in International Patent Document WO 94/01846A, a transformer used as the transmitting device is operated by means of a fixed rectangular waveform having a frequency which is modulated as a function of the energy to be transmitted from the primary to the secondary side. For data transmission in both directions, a high-frequency oscillation is inserted at the rising and falling flanks of the switching signal. The transmission from the primary to the secondary side in this case takes place, for example, at the rising flanks; in the other direction, the transmission takes place at the falling flanks.
The disadvantage of this process is that the data transmission rate in both transmitting devices is limited by the switching frequency of the excitation for the transmitter. In addition, the process is critical in that high-frequency interferences always occur at the switching flanks which may disturb data transmission.
An object of the present invention is to provide a process of the initially mentioned type which is secure with respect to interferences.
This and other objects and advantages are achieved by the process according to the invention, in which the transmission of power takes place by controlling the primary side of the transmitter by a direct-current-free alternating signal. The alternating signal itself is also the carrier of the information from the primary to the secondary side. The coding of the signal transmitted in this direction can be performed by pulse width, amplitude or phase modulation of the alternating signal, preferably by means of a biphase code mode. This code is also free of direct current and is therefore suitable for use as the control signal for the transmitter. The data rate in the given direction is therefore identical to the control frequency of the transmitter.
Data transmission in the reverse direction--in the selected example, from the secondary to the primary side--can be performed by modulating a high-frequency signal (HF-burst), at a frequency of for example two MHz, upon defined points of the primary signal. These points are situated outside the switching flanks of the primary signal, so that no data are transmitted in the area of the switching flanks of the primary side. This ensures that disturbances of the data traffic caused by the switching flanks are not erroneously interpreted as an information signal.
If the transmission in the reverse direction takes place at a frequency which is an even number multiple of the transmission frequency in the first-mentioned direction, the transmission frequency can also be increased in the reverse direction, and a larger quantity of data can be transmitted in this direction. Such an approach is suitable for use in the vehicle steering wheel/steering column example, in which the reverse direction involves the transmission of information which is to be given in the steering wheel and transmitted to the steering column. As a result it is possible to arrange (for example, in the steering wheel) a plurality of switches whose switching condition is easily and accurately transmitted and is converted into a corresponding wiring of the pertaining apparatuses.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.